Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$31.92	3.823%	$33.1403	$33.14	$33.15	$33.10
Purchase #2	$68.32	12.352%	$76.7589	$76.76	$76.75	$76.80
Purchase #3	$34.25	13.580%	$38.9012	$38.90	$38.90	$38.90
Purchase #4	$56.26	5.758%	$59.4995	$59.50	$59.50	$59.50
Purchase #5	$167.67	10.518%	$185.3055	$185.31	$185.30	$185.30
Purchase #6	$210.75	3.186%	$217.4645	$217.46	$217.45	$217.50
Purchase #7	$179.94	4.292%	$187.663	$187.66	$187.65	$187.70
7 purchase totals =	$749.11		$798.7329	$798.73	$798.70	$798.80